Curved TV = Waste of time, marketing Gimick and they dont sit flat on the wall. I always want my TV as close to wall as possible, hence my 7mm bracket!
3D = Waste of time
4K = Looks good but content is lacking, so if you go for it (especially with the size you are condisering) get one that upscales from Full HD to 4K really well.
However if I was you I would consider another option. Get a Medium size TV, around 50in which is great quality for everyday viewing. Then get a projector and screen for movies and Sports. It is totally worth it and with your budget more than possible,
Just think about it, when you watch everything on 73in, BBC news, Doctor Who, Eastenders etc you get used to watching it all at 73in. Then you put on a movie and it is actually smaller than watching the news, because you get those stupid letterbox lines for the widescreen format most films are shot in. For me the main reason for home cinema is for it to imerse you into the movie, but if the screen is the same size as all normal TV you watch its just the norm and you loose the impact.
The right projector can give you a 100+in screen easily.
Just my 2 pence worth.